This invention relates to methods of measuring temperature and apparatus for use therewith. More especially, the invention relates to a method of and apparatus for measuring the temperature of a liquid, gas or solid body from which electromagnetic radiation in the near infra-red, visible, and ultraviolet regions is emitted. Examples of such liquids include a melt of, for example, molten steel held in a ladle furnace; molten iron or steel being teemed from, for example, a ladle or tundish; and molten glass or aluminium retained in a heating vessel. Examples of solids include steel slabs, sheets or ingots; and continuously cast metal strands. The temperature of flowable material such as incadescent powders, for example lime, can also be measured.
For the sake of convenience--but not by way of limitation--the invention will be introduced and described with reference to ladle steelmaking.
A ladle steelmaking process includes the steps of heating and adjusting the composition of molten steel in a ladle, the steel having been produced in for example, an electric arc furnace or a basic oxygen vessel. The ladle of molten steel is covered and placed in a heating station where the steel is heated to a predetermined temperature by, for example, arcs sustained by one or more graphite electrodes. A layer of slag is applied to the steel surface to refine the steel and to enhance the efficiency of energy transfer from the arcs to the steel melt.
The steel in the ladle is stirred by, for example, bubbling an inert gas through it or by magnetic induction, to maintain homogeneity of temperature and composition. The stirring mechanism gives an upward thrust to a localised column of steel in the ladle which, depending upon the stirring power, raises an area of the steel surface above the slag cover. The area of exposed steel is commonly referred to as the steel "eye" in the slag layer.